spinal implant systems provide a rod for supporting the spine and for properly positioning components of the spine for various treatment purposes. Bolts, screws, and hooks are typically secured to the vertebrae for connection to the supporting rod. These vertebral anchors must frequently be positioned at various angles due the anatomical structure of the patient, the physiological problem being treated, and the preference of the physician. It is difficult to provide secure connections between the spinal support rod and these vertebral anchors at all the various angles and elevations that are required, especially where there are different distances between the rod and bolts and where these components are located at different heights on the patient.
One solution to this problem is shown in U.S. Pat. No. 5,938,663 to Petreto, the disclosure of which is specifically incorporated into this specification by reference. This patent describes a connection between a rod and a vertebral anchor, through which a surgeon may vary the angle between a spinal rod and the anchor to which the rod is attached. The connection is equipped with a ball joint that allows the surgeon to fix the desired angle between the anchor and the rod. This system, however, has no elevation adjustment capability after the bone anchor is installed because the clamp in that invention must be secured between a nut and an immovable shoulder on the bone anchor.
What is needed is a connection assembly between a spinal rod and a vertebral anchor that allows the surgeon to fix the desired elevation between a rod and the bone anchor as well as fix the desired angle between the anchor and rod. The following invention is one solution to that need.